Reconstructing the Growth History of a Salt-Influenced Rift Basin to Predict Sandbody Distribution and Architecture, South Viking Graben, Northern North Sea

Kane, Karla E.¹, Eirik Larsen², Christopher A.L. Jackson³, Anna Sofia Gregersson⁴ (1) Imperial College, London, United Kingdom (2) Statoil ASA, Stavanger, Norway (3) Imperial College, (4) Statoil ASA,

In the Sleipner area of the South Viking Graben, salt tectonics and the growth of normal faults combined to form a series of interconnected sub-basins into which deep-water sediments were deposited in late syn-rift times. Reconstructing the tectono-stratigraphic history of this structurally complex area is critical in assessing the potential for deposition of deep-water, sand-prone reservoir intervals within the largely unexplored Upper Jurassic syn-rift succession.

Mapping of key seismic horizons allows the syn-rift succession to be sub-divided into two major seismic-stratigraphic units that document tectonically-controlled changes in depocentre location and size. Within and between individual sub-basins the lowermost syn-rift interval thins towards salt-cored highs, revealing a period of syn-depositional diapirism. The uppermost syn-rift interval displays significant spatial variations in thickness which are related to both ongoing diapirism and newly active normal faults.

Biostratigraphic and wireline data on structural highs that flank the sub-basins suggest that periods of erosion on these highs correspond to expanded, possibly sand-prone, intervals within the basin-fill succession. Although no well data is available within the basin-fill itself, the identification of an unconformity within the uppermost syn-rift interval may reflect gravity-flow-related submarine erosion associated with “fill-and–spill” of sediment between component sub-basins. Seismic attribute analysis provides supporting evidence for the existence of such a system.

Preliminary results predict structurally-confined sandbodies within the Sleipner sub-basins, sourced from the basin-margin and deposited in an axial turbidite lobe system. There is also potential for a series of smaller slope apron systems, sourced from the uplifted footwalls of active normal faults.